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Can You Trust Your Calorie Counter?

Whether it's the number of calories on the nutrition facts label or the readout on your Fitbit, chances are those calories counts are wildly inaccurate. So, what's the point of paying attention to calories?  Nutrition Diva explains.

By
Monica Reinagel, MS, LD/N, CNS
6-minute read
Episode #520

Calorie Estimates Can Be Inaccurate

Let's say you plug your details into an online calculator and learn that you use 1847 calories per day. Take that number with a truckload of salt. Energy expenditure varies hugely from person to person. Even if you and I are the exact same height, weight, age, and sex and do the exact same workout, you may burn 400 calories more or less than I do. 

Energy needs can be affected by diet, genetics, body composition, hormones, drugs, and a million other factors. And just to make the whole situation a little more ridiculous, those readouts on your treadmill, Peloton, fitwatch, or diet tracker that tell you how many calories you burn doing various activities are only slightly more accurate than asking the Magic 8 Ball.

But wait, there's more.

Those readouts on your treadmill, Peloton, fitwatch, or diet tracker that tell you how many calories you burn doing various activities are only slightly more accurate than asking the Magic 8 Ball.

Calorie Counts for Foods Are Also Unreliable

The numbers listed in your your calorie counting app represent average values for foods. Even if you are measuring or weighing your food with great precision, this apple may be a bit sweeter than average, that banana might be a little less ripe, this nut may have a bit more fat.  Even for packaged and processed foods, the calorie count shown on the Nutrition Facts label is just an average. A variation of +/- 10% would not be surprising.

Secondly, those calorie counts are estimated using formulas that may or may not be 100% reliable. It was recently discovered, for example, that the standard formulas that were in use for most of the last 100 years over-estimated the amount of energy that humans are able to liberate from nuts. More modern methods suggest that almonds provide about 20% less energy or calories than previously thought.

Finally, our bodies are not bomb calorimeters. Like a campfire that might go out and leave a few unburned chunks of wood, our bodies don’t extract all the energy from our food. Some unknown and variable amount of that energy will pass through us unabsorbed. 

So What’s the Point of Paying Attention to Calories?

Once you realize how fuzzy these numbers are, it’s clear that there’s really no point in counting every calorie. So, how are we supposed to know how much to eat? Can we just rely on our hunger or satiety signals to tell us if we need food and when we’ve had enough? Probably not.

See also: Is Intuitive Eating the Answer to Weight Loss?

There are so many foods available that are literally engineered to override our satiety signals. Advertising, habit, and social cues can trigger feelings of hunger even when we are not even remotely in need of food. For most of us, deciding when, what, and how much to eat in the modern world requires some prefrontal cortex activity. And here's where calorie counters might come in handy.

See also: How to Tell If You're Really Hungry

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About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.